The present invention relates in general to adjustable seats and in particular to motor vehicles seats of the type and which include a seat frame adjustable in longitudinal direction and in vertical direction independently on the front part of the seat and on the rear part of the seat and also having reclinable backrest. Each of these adjusting movements is carried out by a separate adjuster and all adjusters being driven by a single driving motor via a power distributing device. The power distributing device is selectably oscillated by a plurality of couplings controlled by a control device.
Known are power distributing gears for seats of the aforedescribed type in which the control unit for the distributing gears is formed by a solenoid. Such solenoids have an annular configuration and are fixedly arranged in the housing of the distributing gear unit. Each of the solenoids cooperates with an assigned driving shaft of an adjuster in such a manner that when a current flows through the solenoid, the latter shifts a coupling disc which is axially displacable on the shaft but supported for joint resilator, into engagement with a gear supported for free rotation on the driving shaft. In other words, in prior art, power distributing gear units for driving shafts are arranged side by side in such a manner that at least two of the shafts are permanently in mesh with the pinion of the driving motor whereas the gears pertaining to the other driving shafts are in mesh with the first mentioned gears. Since all of the gears are supported for free rotation on respective driving shafts, the transmission of rotary movement takes place only via those driving shafts the solenoids of which are energized to couple the corresponding coupling discs with the opposite gear on the shaft. As soon as the solenoid is deenergized, a pressure spring arranged between the gear and the coupling disc disengages the latter and consequently the rotary movement from the gear is no longer transmitted to the driving shaft. The driving shaft can be connected to the assigned adjuster in the seat frame or in the backrest mount by means of flexible shafts for example. By switching on solenoids assigned to selected driving shafts, each of the adjusters can now be activated by a single driving motor and a separate drive for respective adjusters can now be dispensed with.
Such known electromagnetically controlled means for a power distributing gear unit are however, relatively expensive especially for the mass production as used in contemporary car industry. In addition, due to the heavy duty solenoids, the gear distributing unit has a very high weight. In addition, to install the solenoids in the housing of the unit, the installation room must be increased. In construction of motor vehicle seats however, the cost, weight, and installation space considerations are of substantial importance.